This is an example of 3 different ways to use Node.js to process big data files. One file is the Node.js' fs.readFile(), another is with Node.js' fs.createReadSteam(), and the final is with the help of the NPM module EventStream.
There is also use of console.time and console.timeEnd to determine the performance of the 3 different implementations, and which is most efficient processing the files.
Download the large file zip here: https://www.fec.gov/files/bulk-downloads/2018/indiv18.zip
The main file in the zip: itcont.txt, can only be processed by the readFileEventStream.js file, the other two implementations can't handle the 2.55GB file size in memory (Node.js can only hold about 1.5GB in memory at one time).*
*Caveat: You can override the standard Node memory limit using the CLI arugment max-old-space-size=XYZ. To run, pass in node --max-old-space-size=8192 <FILE NAME>.js (this will increase Node's memory limit to 8gb - just be careful not to make it too large that Node kills off other processes or crashes because its run out of memory)
Before the first run, run npm install from the command line to install the event-stream and performance.now packages from Node.
Add the file path for one of the files (could be the big one itcont.txt or any of its smaller siblings in the indiv18 folder that were just downloaded), and type the command node <FILE_NAME_TO_RUN> in the command line.
Then you'll see the answers required from the file printed out to the terminal.
Use one of the smaller files contained within the indiv18 folder - they're all about 400MB and can be used with all 3 implementations. Run those along with the console.time and performance.now() references and you can see which solution is more performant and by how much.